1. Field of the Invention
The present invention relates to a process for producing a semiconductor memory device, and, more particularly to a semiconductor memory device employing the structure of a charge coupled device, hereinafter referred to as a CCD.
2. DESCRIPTION OF THE PRIOR ART
Recently, attention has been concentrated upon employing CCD's to memory devices.
In the general structure of CCD, for example a three phase CCD, one gate electrode and a plurality of three electrode sets for transferring electric charges are successively arranged on the top surface of an insulating material, which covers the semiconductor material substrate. The electrodes of the CCD, usually produced by a photolithographic process, are separated by equidistances, preferably of from 2 to 3 microns. That is, the material for the elctrodes, such as aluminum, is placed on the insulating material and then is covered by a photo-resistant layer. A photolithographic pattern is then drawn on the photo-resistant layer so as to allow selective removal of this layer and the aluminum from the substrate. Due to the selective removal of the aluminum, individual aluminum electrodes are produced. Since the distance between two electrodes is dependent upon the accuracy of the photolithographic technique, the memory density of the CCD is limited thereto.